1. Field of the Invention
The present invention relates to the field of the clinical analysis of blood, and in particular to a composition comprising human plasma, buffered isotonic solution and ferulic acid to be used as the abnormal coagulation control in haemostasis, coagulation and fibrinolysis assays. The present invention also relates to the use of ferulic acid in the preparation of abnormal control plasma in haemostasis assays.
2. Description of the Related Art
Haemostasis is the group of mechanisms which prevent animals that have a vascular system from bleeding out following an injury. The haemostasis mechanism has a variety of important functions: (a) keeping the blood in a fluid state when it flows through the vascular system, (b) stopping bleeding at the site of a wound or wherever there is blood loss, by forming a clot, and (c) ensuring the clot is removed once the wound has healed. Typically, five elements are involved in haemostasis, namely: the blood vessels, platelets (cell component), coagulation factors, coagulation inhibitors and the fibrinolytic system. Haemostasis thus involves a group of forces which have to interact in perfect balance—procoagulant forces and anticoagulant forces. This balance is controlled by various proteins, some of which are known as coagulation factors. It is a very delicate balance where any imbalance could lead to either a prothrombitic state or a blood disorder.
It is very important to precisely measure coagulation function because any impairment that is present could be life-threatening. This becomes particularly important in patients who undergo coagulation therapy in thromboembolic conditions.
The role of the haemostasis laboratory is to detect and recognise physiological changes in haematological and thrombotic diseases. To do so, various assays are used, such as primary haemostasis assays, coagulometric assays and immunological assays, which allow useful information to be obtained in order to help health professionals make a precise diagnosis and devise suitable treatment therefor.
Haemostasis assays can be divided into two distinct groups: initial haemostasis assessment, which can include the prothrombin time (PT), activated partial thromboplastin time (aPTT), determination of fibrinogen concentration, and thrombin time (TT); and the other group, which can include specific assays such as reptilase time (RT), activated coagulation time (ACT), and determination of the concentration of antithrombin (AT), protein C, protein S, von Willebrand factor, plasminogen and α2-antiplasmin (plasmin inhibitor).
In haemostasis laboratories, patient samples are analysed for a wide variety of haemostasis screens and specific assays throughout the working day. In these assays, methodological control of the variables that affect the efficiency and efficacy of the haemostasis assays is essential for a correct diagnosis. The use of control plasmas plays an important role in these internal quality controls carried out by laboratories.
It is highly recommended to use, at regular intervals, one control in the normal coagulation time range and another in the abnormal range to ensure the proper functioning of the reagents and devices used in the haemostasis laboratory. Recommendations have been published regarding the frequency with which control materials should be tested for some coagulation assays. For example, the Clinical and Laboratory Standards Institute (CLSI) has published guidelines relating to the PT and aPTT assays. Said documents recommend testing, at least, two levels of control materials every 8 hours, or more frequently if samples are processed in a continuous manner as is the case in many laboratories. This document from the CLSI also indicates that the control sample should be used in the first assay that is carried out following a change of reagent or the inclusion of new reagents or following a significant apparatus change. The controls allow for the assessment of the analytical precision and deviation of both the coagulation assays in the coagulometer system employed and the reagents used.
Literature has been published relating to the preparation of coagulation control plasma, and some of these plasmas are currently commercially available. However, the majority of the methods described are time-consuming and include expensive steps for the absorption of critical plasma protein factors to obtain the abnormal coagulation properties. One method for preparing abnormal coagulation control plasma comprises incubating normal plasma with aluminium hydroxide and then centrifuging said plasma. The sediment contains various coagulation factors and the resultant supernatant can be used as pathological control plasma. Abnormal clotting times are achieved by removing the coagulation factors from the plasma. However, the coagulation control plasma thus obtained is not completely satisfactory, since abnormal results are obtained in some assays whilst in others, for example factors VIII, XI and XII, as well as in other haemostasis assays such as TT and RT, the activity is within the normal range.
Another method for producing an abnormal coagulation control is to dilute normal plasma. Said method is described in an international guide (NCCLS H30-A2), which mentions how to prepare an abnormal control plasma for determining fibrinogen according to the Clauss method. Said document also describes how a series of normal plasmas can be diluted with a barbital buffer to obtain plasma having an abnormal result (low fibrinogen content). The final result of the dilution of a series of normal plasmas is abnormal in the majority of the haemostasis assays. However, said coagulation control plasma is not abnormal for TT and RT for example. The same result is obtained by diluting the normal plasma with other solutions, such as a 4% albumin solution.